I did not analyzed Phlgopite of GDH-52. I have data on Ilmenites of GDH 52, it contains more than 54% TiO2. Is it from 52?

Thanks for your query. Yes, your idea is correct. I am looking for appropriate reason of such high Ti in phlogopite. I’ve already got some interesting Ti-substitution mechanism for enrichment of Ti in studied phlogopite. Still I am doubt about those Ti-substitution mechanisms which one really taken place for enriched Ti in phlogopite. The structural formulae show that these phlogopites are characterized by a deficiency in octahedral site occupancy and by possessing insufficient Si and Al to fill the tetrahedral site completely. Normally the octahedral site deficiency is due to the creation of lattice vacancies where Ti4+ substitutes for 2Mg2+ (Forbes and Flower, 1974; Robert, 1976) and also have suggestions that the incorporation of Ti4+ at octahedral sites results in the creation of octahedral vacancies and introduction of Mg2+ to tetrahedral sites.

Examples VIMg2++IVSi4+=VITi4++VIMg2+ (Robert, 1981)

2VIMg2+=VITi4++VI□ (Forbes and Flower, 1974).

So, I am doing some works on this substitution and searching for more information. Thank you again.

When you will comeback in Bangladesh, we will discuss. I have some EPMA data of other minerals like olivine, clino-pyroxene, feldspar, apatite and ilmentie. Mineralogically the rock contains about 9-12% ilmenties. May be due to concentration of TiO2 in Phlogopites, the color of phlogopite also more golden and attractive. 

Thank you for your reply. Yes, really the color of phlogopite is so attractive and makes me more inquisitive. We'll discuss all after my return back.